DTC 14

DTC 14:

ECT Sensor Circuit:

CIRCUIT DESCRIPTION:
The coolant temperature sensor is a thermistor (a variable resistor that changes along with coolant temperature) in series with a fixed resistor in the ECM. The ECM applies 5.0 volts to the sensor. The ECM monitors the voltage across the coolant temperature sensor and converts it into a temperature reading. When the engine is cold, the sensor resistance is high, therefore, the ECM will see high signal voltage. As the engine warms, the sensor resistance becomes less, and the ECM will read a low voltage input. DTC 14 will set if the following condition is met for at least 3 seconds; Voltage input at the ECM indicates a coolant temperature below -48°C (-54°F).

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. This test simulates a DTC 15. If the ECM stores a DTC 15, the ECM and wiring are OK and the coolant temperature sensor is faulty. If DTC 14 repeats, the coolant temperature sensor is OK and the wiring to the ECM or the ECM if faulty.

2. This test determines whether there is an open in the GRY/WHT or LT GRN/BLK wires, a short to B+ in the GRY/WHT wire or a faulty ECM.

DIAGNOSTIC AIDS:
After engine is started the temperature should rise steadily to about 95°C (203°F) then stabilize when thermostat opens. DTCs 14, 23 and 32 stored at the same time could be the result of an open LT GRN/BLK sensor ground wire. When replacing the coolant temperature sensor the "Temperature to Resistance Value" scale on the chart may be used to test the coolant temperature sensor at various temperature levels to evaluate the possibility of a "shifted" (mis-scaled) sensor. A "shifted" sensor could result in poor driveability complaints.